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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"><html><head><title>SQLite Query Language: DELETE</title><style type="text/css">body { margin: auto; font-family: "Verdana" "sans-serif"; padding: 8px 1%;}a { color: #45735f }a:visited { color: #734559 }.logo { position:absolute; margin:3px; }.tagline { float:right; text-align:right; font-style:italic; width:240px; margin:12px; margin-top:58px;}.toolbar { font-variant: small-caps; text-align: center; line-height: 1.6em; margin: 0; padding:1px 8px;}.toolbar a { color: white; text-decoration: none; padding: 6px 12px; }.toolbar a:visited { color: white; }.toolbar a:hover { color: #80a796; background: white; }.content { margin: 5%; }.content dt { font-weight:bold; }.content dd { margin-bottom: 25px; margin-left:20%; }.content ul { padding:0px; padding-left: 15px; margin:0px; }/* rounded corners */.se { background: url(images/se.png) 100% 100% no-repeat #80a796}.sw { background: url(images/sw.png) 0% 100% no-repeat }.ne { background: url(images/ne.png) 100% 0% no-repeat }.nw { background: url(images/nw.png) 0% 0% no-repeat }</style><meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head><body><div><!-- container div to satisfy validator --><a href="index.html"><img class="logo" src="images/SQLite.gif" alt="SQLite Logo" border="0"></a><div><!-- IE hack to prevent disappearing logo--></div><div class="tagline">Small. Fast. Reliable.<br>Choose any three.</div><table width=100% style="clear:both"><tr><td> <div class="se"><div class="sw"><div class="ne"><div class="nw"> <div class="toolbar"> <a href="about.html">About</a> <a href="sitemap.html">Sitemap</a> <a href="docs.html">Documentation</a> <a href="download.html">Download</a> <a href="copyright.html">License</a> <a href="news.html">News</a> <a href="http://www.sqlite.org/cvstrac/index">Developers</a> <a href="support.html">Support</a> </div></div></div></div></div></td></tr></table> <a href="lang.html"> <h2 align="center">SQL As Understood By SQLite</h2></a><h1>DELETE</h1><h4><a href="syntaxdiagrams.html#delete-stmt">delete-stmt:</a></h4><blockquote> <img src="images/syntax/delete-stmt.gif"></img> </blockquote><h4><a href="syntaxdiagrams.html#qualified-table-name">qualified-table-name:</a></h4><blockquote> <img src="images/syntax/qualified-table-name.gif"></img> </blockquote><p>The DELETE command is used to remove records from a table.The command consists of the "DELETE FROM" keywords followed bythe name of the table from which records are to be removed.</p><p>Without a WHERE clause, all rows of the table are removed.If a WHERE clause is supplied, then only those rows that matchthe expression are removed.</p><a name="trucateopt"></a><p>When the WHERE is omitted from a DELETE statement and the tablebeing deleted has no triggers,SQLite uses an optimization to erase the entire table contentwithout having to visit each row of the table individual.This "truncate" optimization makes the delete run much faster.Prior to SQLite <a href="releaselog/3_6_5.html">version 3.6.5</a>, the truncate optimizationalso meant that the <a href="c3ref/changes.html">sqlite3_changes()</a> and<a href="c3ref/total_changes.html">sqlite3_total_changes()</a> interfacesand the <a href="pragma.html#pragma_count_changes">count_changes pragma</a>will not actually return the number of deleted rows. That problem has been fixed as of <a href="releaselog/3_6_5.html">version 3.6.5</a>.<p>The truncate optimization can be disabled for all queries by recompilingSQLite with the <a href="compile.html#omit_truncate_optimization">SQLITE_OMIT_TRUNCATE_OPTIMIZATION</a> compile-time switch.</p><p>If SQLite is compiled with the <a href="compile.html#enable_update_delete_limit">SQLITE_ENABLE_UPDATE_DELETE_LIMIT</a>compile-time option, then the syntax of the DELETE statement isextended by the addition of optional ORDER BY and LIMIT clauses:</p><h4><a href="syntaxdiagrams.html#delete-stmt-limited">delete-stmt-limited:</a></h4><blockquote> <img src="images/syntax/delete-stmt-limited.gif"></img> </blockquote><p>The optional LIMIT clause can be used to limit the number ofrows deleted, and thereby limit the size of the transaction.The ORDER BY clause is used only to determine which rows fallwithin the LIMIT. The order in which rows are deleted is arbitraryand is not determined by the ORDER BY clause.</p><p>The presence of a LIMIT clause defeats the truncate optimizationcausing all rows being deleted to be visited.</p><hr><small><i>This page last modified 2009/01/02 16:47:13 UTC</i></small></div></body></html>⌨️ 快捷键说明
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